Ans:

(i) Serial: The most basic way to organize the collection of records that from a five is to use sequential organization. In a sequentially organized file record are written consecutively when the file is created and most be accessed consecutively when the file is later used for input.

The basic advantage offered by a sequential file is the easy of access to the next record the simplicity of organization and the absence of auxiliary data structures.

(ii) Index Sequential - The retrieval of a record from a sequential file, on average, requires access to half the records in the file, making such enquiries not only inefficient but very time consuming for large files.

(iii) Hashes - It is a Direct file organization. In direct file organization the key value is mapped, directly to the storage location. The usual method of direct mapping is by performing some arithmetic manipulation of the key value. This process is called hashing.